As the third generation of rare earth permanent magnet materials, Nd—Fe—B features high residual magnetism Br, high coercive force Hcj and high magnetic energy product (BH)m. What's more, it does not contain the strategic element Co. So, it makes market immediately once such features are discovered, and becomes one of the key materials for modern science and technology development, like computer, IT, aerospace engineering, communication, transportation, office automation, household appliance and healthcare.
Compared with the second generation of SmCo magnet, Nd—Fe—B magnet has relatively great cost advantage. But its cost is still higher compare with ferrite magnet, wherein metal Nd takes 90% or above of the costs of the raw materials. With the constant growth of rare earth magnet yield all over the world, the utilization amount of metal Nd increases greatly, imposing great pressure on magnetic material manufacturers and users. To solve the problem, we invented this low-neodymium and high-performance magnet containing no heavy rare earth element and its preparation method, which has great practical meaning.
Beside Nd, metal elements of La and Ce within the natural rare earth resources features rich reserve and low cost. But, the magnetic torque Js and anisotropic field HA of La2Fe14B/Ce2Fe14B falls far below that of Nd2Fe14B and it is impossible to meet user's requirements on product performance when they are applied solely. In research work for substituting Nd partially by Ce, the Central Steel & Iron Research Institute under Ministry of Metallurgical Industry and Magnequench (Tianjin) Co., Ltd. respectively filed Chinese patents applications, Publication numbers CN1035737A and CN101694797. According to the method stated in the above patents/applications, the alloys containing multiple kinds of compositions need to be smelted for manufacturing different series and grades of magnets and the production costs are increased greatly. Besides, the residual magnetism, coercive force and magnetic energy product of the magnet prepared as the above patents/applications methods are relatively low. The reason is that Ce is smelted directly into the alloy, which leads to the Nd in the main phase dominantly substituted by Ce and worsens the properties of the magnets produced. In addition, For the preparation processing, as the sintering temperature of the magnet is above 1060° C., the grain size will grow large easily. As a result, the magnetic performance will be worsened and the magnet production costs will be increased.